Problem with PgTcl auditing function on trigger

Glyn Astill wrote:

Hi people,

I've tried posting on the general list about this, but I never get
a
reply, so I'm trying here.

I think you'll probably have more luck with a TCL list than the PG
hackers list. However, I've attached some pltcl functions I put together
ages ago to do this sort of thing. Hopefully that will help you.

--
Richard Huxton
Archonet Ltd

----- Original Message ----
From: Glyn Astill <glynastill@yahoo.co.uk>
To: pgsql-hackers@postgresql.org
Sent: Friday, January 4, 2008 5:23:18 AM
Subject: [HACKERS] Problem with PgTcl auditing function on trigger

Hi people,

I've tried posting on the general list about this, but I never get
a
reply, so I'm trying here.

I have a function that is run each time an INSERT, DELETE or UPDATE
happens on a row and log into an audit table.

It is based on the info here:

http://www.alberton.info/postgresql_table_audit.html

We have a table Customers.CREDIT with a primary key "NUMBER",
"TRANSNO", "RECNUM".

I have a trigger as follows:

CREATE TRIGGER "tg_audit_credit"
AFTER INSERT OR DELETE OR UPDATE ON "Customers"."CREDIT"
FOR EACH ROW
EXECUTE PROCEDURE "log_to_audit_table" ();

This uses the attached tcl function which basically runs this for a
delete

spi_exec -array C "INSERT INTO audit_table(ts, usr, tbl, fld,
pk_name, pk_value, mod_type, old_val, new_val)
VALUES (CURRENT_TIMESTAMP, '$tguser', '$tgname',
'$modified_field',
'$pk_name', '$pk_value', '$TG_op', '$previous_value', NULL)"

The function works fine for this SQL statement

delete from "CREDIT" where "TRANSNO" < 11148188 AND "TRANSNO" >
11148180;

However if I try this one I get a syntax error.

delete from "CREDIT" where "RECNUM" < 2484907 AND "RECNUM" >
2484905;

Is the Tcl function the same for RECNUM and TRANSNO? I noticed you have
set pk_name "RECNUM" ...

Not sure if you are changing this when you run the different DELETEs.

The error is below. Do I need to escape my strings? And if so how
do
I do this?

Thanks
Glyn

SEE=# delete from "CREDIT" where "RECNUM" < 2484907 AND "RECNUM" >
2484905;
ERROR: syntax error at or near "S"
CONTEXT: syntax error at or near "S"
while executing
"spi_exec -array C "INSERT INTO audit_table(ts, usr, tbl, fld,
pk_name, pk_value, mod_type, old_val, new_val)
VALUES (CURRENT_TIMESTAMP, '$tguser', '$t..."
("foreach" body line 5)
invoked from within
"foreach field $TG_relatts {
if {! [string equal -nocase [lindex [array get OLD $field] 0]
$pk_name]} {
set modified_field [lindex [array get..."
("DELETE" arm line 11)
invoked from within
"switch $TG_op {
INSERT {

#get PK value
foreach field $TG_relatts {
if {[string equal -nocase [lindex [array get NEW $field] 0]
$pk_name]} {..."
(procedure "__PLTcl_proc_5667381_trigger_16644" line 23)
invoked from within
"__PLTcl_proc_5667381_trigger_16644 tg_audit_credit 16644 CREDIT
Customers {{} RECNUM TRANSNO NUMBER EXMON EXYEAR OLDTICK COACHES
VALUE POSTAGE DEPOSIT..."

I'm not sure where the error is coming from, off hand. The only thing
I can think of now is that you may need to [quote] the values or
use spi_execp instead. Perhaps there is a ' in there somewhere causing problems.

As a side note, just some tips (i realize that you got this from the link above):

You have several instances of constructs such as:

if {! [string equal -nocase [lindex [array get NEW $field] 0] $pk_name]} {

but this really is just $field...so you don't need all of that. You can just do:

if {! [string equal -nocase $field $pk_name]} {

Similiarily, you have this construct
set pk_value [lindex [array get NEW $field] 1]

But you can use this instead:
set pk_value $NEW($field)

And then, this whole block:

foreach field $TG_relatts {
if {[string equal -nocase [lindex [array get NEW $field] 0] $pk_name]} {
set pk_value [lindex [array get NEW $field] 1]
break;
}
}

Not sure the purpose here, but you should be able to just do:

if {[info exists NEW($pk_name)]} {
set pk_value $NEW($pk_name)
} else {
# something went wrong here...need this if there's a chance $pk_name might not be there
}

Note also that TG_relatts has an empty element as the first element of the list, so this
if {! [string equal -nocase [lindex [array get OLD $field] 0] $pk_name]} {

may be giving you trouble, since it won't catch the empty element.

so, you could write that particular loop construct as such:
foreach field [lrange $TG_relatts 1 end] {
if {! [string equal -nocase $field $pk_name]} {
set modified_field $field
set previous_value $OLD($field)
spi_exec -array C "INSERT INTO audit_table(ts, usr, tbl, fld, pk_name, pk_value, mod_type, old_val, new_val)
VALUES (CURRENT_TIMESTAMP, '$tguser', '$tgname', '$modified_field', '$pk_name', '$pk_value', '$TG_op', '$previous_value', NULL)"
}
}

You may to throw some [elog]'s in there, to see what's going on as well.

HTH,
--brett

____________________________________________________________________________________
Looking for last minute shopping deals?
Find them fast with Yahoo! Search. http://tools.search.yahoo.com/newsearch/category.php?category=shopping